Incandescent lamp.



W ASHBURN.

INGANDESGBNT LAMP.

APPLIUATIO K FILED JAN. 11 1908.

Patented Nov. 14, 1911.

SAMUEL D. WASHBURN, OF BOSTON, MASSACHUSETTS, ASSIGNOB OF TED STATES. PATENT OFFICE.

ONE-HALF TO THE IN-EB GLOBE LAMP COIVIPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF I MASSACHUSETTS.

INCANDESCENT LAMP.

Patented Nov. 14, 1911;

I Application filed January 11, 1908. Serial No. 410,331. I

Specification of Letters Patent.

To all whom it may concem:'

Be it known that I, SAMUEL D. WASH- BURN, a citizen of the United States, and a resident of Boston, in the county of Sufiolk and State of Massachusetts, have invented an Improvement in Incandescent Lamps, of which the following description, in connection with the accompanying drawing, is a specification, like letters on the drawing representing like parts.

This invention relates filament part of an electric incandescent lamp to enable the distribution of the-light in the most useful direction and at the same- 3 is a bottom plan view 0 shown in Figs. 1 and 2.

The shape of the filament of this invention is that of two connected conical spirals, each spiral being exterior of and not overlapping the other. One limb of the filament starting from one leading-in wire is-shape to form one spiral, and the other limb start- 'ing from the other leading-in wire is shaped .to form the other spiral; the two limbs being continuous the spirals are of course connected at their bases. By this construction thetwo spirals are supported very nearly f the filamentform of bulb provided with a reflector. Fig. i

timeto be such that it can be easily and from their centers of gravity, thus securing cheaply manufactured. I a rigidand graceful support, and the entire It is not claimed that it is broadly novel length of the filament radiates its light to- 4 and .withouta reflector;

to change the distribution of the light by changing the shape of the filament, because in Patent No. 654,207, granted July 24, 1900, is shown an early attempt to obtain a shape which would give a downward, or tip istribution of the light. In making the filament shape shown in this patent it was found that the short sharp curves made the filament so fragile that the break ge was excessive, an it was also found that the arts of the filament were so close together that the heat from one part tended to overconical spiral and that each one of these heat the 0 her parts and thus finally destroy the filament. spirals is exterior to the other and that in In the present invention these difiiculties each spiral the filament turns in the direction of the hands of a clock to form its spiral'. But it is obvious that it is not essential whether one or both of the spirals turn clockwise or counter clockwise.

In this invention the distance from any part of the filament to its nearest adjacent part is as great as possible because of the have been overcome and a filament produced in which the parts of the filament do not lie close enough together to produce injurious overheating, and in which the parts are ar. ranged in difierent planes.

The distribution of light in a downward direction or toward the tip is what is most desired, and the filament of this invention 18 varying planes of the spiral, and thus overso shaped as to secure a maximum distribulapping effects are minimized. tion of the light in such direction. The spirals of this invention may take the form of any mathematical or irregular curve, or be such as would result if formed over a true cone, a distorted cone, or some odd shaped form, so long as they have the essential quality of a spiral, viz., a gradual change in diameter, so that when viewed from the base substantially the entire filament is displayed.

In the drawings In thisinvention the ends of the filament constitute the terminals of connected conical spirals, and thus support the body part of the filament at points very near the centers of gravity, thus giving a rigid as well as a graceful support.

The drawings show the invention in its preferred form applied both to a bulb with V I the filament is ,shown as ective-view of a lamp Figure l is' apersp placed an exhausted bulb with its ends containing one form-of the invention whereconnected to theleading-1n w1res. in the bulbis withoutfla reflector. Fig. 2 is a The construction of" a lamp is $0 well view similar toFig; 1 showing a different I known to those skilled in the art of making 5 mon shaped form without a reflector, and

10 vided with a reflector is shown in Fi 2 a r v a 1,008,983

nected-conical spirals, each exterior of the other, whereby a maximum distribution of light is secured in a direction perpendicular to the bases of the spirals.

2. electric incandescent lamp compris- 25 inga filament, the limbs of whic are each shaped to form a clockwise conical spiral, the said spirals being I connected at their lamps that any further description of the manufacture of the lamp or the filament is unnecessary. InFig.-' 1 the lamp is shown of the com- 3 In such a sha by means of this invention a very valuab e distribution of light can be obtained downward or toward the tip.

J The more expensive form of lamp proand'the invention is, of course, equallya a t able to this form, and when combined wlth a reflector a still more durable distribution of light'in a downward direction or toward bases of the spirals. i

In testimony whereof, I have signed "my name to this specification, in the presence of two subscribing witnesses.

SAMUEL D. WASHBURN.

Witnesses:

THOMAS J. DRUMMOND, NATHAN HEARD.

15 the tip is secured. p

, Having described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. An electric incandescent lamp com- 20 prising a filament shaped to form two con- 

